Group A streptococcus (GAS)-induced toxic shock syndrome (TSS) in pregnancy is rare, but its clinical course is fulminant. The mortality rates of mother and fetus are reported to be 58 and 66%, respectively. We report a case of GAS-TSS after cesarean section. A 38-year-old pregnant woman of 38 weeks gestation was admitted to our hospital because of vomiting, fever of 39 degrees C, and continuous abdominal pain with scanty genital bleeding. She had complained of sore throat several days before. One hour after admission, external fetal monitoring revealed periodic pulse deceleration to 90 x beats min(-1). The emergent cesarean section was performed under general anesthesia. Approximately 8 hours after the cesarean section, she developed coma, shock and respiratory insufficiency requiring intubation. Streptococcus pyogens were isolated from her blood sample and the patient met criteria for GAS-TSS. She was treated with antibiotics (penicillin and clindamycin), antithrombin III, recomodulin, catecholamins, and continuous hemodialysis with filtration of toxins. Although the patient recovered and was discharged on 63rd day, the infant died on postpartum day 4. Early recognition and intensive treatment for GAS is recommended in a late stage pregnancy with an episode of sore throat, vomiting, high fever, strong labor pain, and DIC signs.